1. Field of the Invention
The present invention relates generally to the operation of a hybrid electric vehicle, and more particularly, to a diagnostic system and method for validating engine and motor velocities in a vehicle.
2. Background Art
A number of different types of vehicles include one or more electric motors and/or generators in addition to an internal combustion engine. For example, a hybrid electric vehicle may have a separate motor and generator, or a single unit in which the motor and generator are combined, in addition to a gasoline or diesel internal combustion engine. Other vehicle architectures may similarly include an engine and one or more electric motors. As the number of torque generating devices increases, control of such vehicles becomes increasingly complex.
Effective control of a vehicle having a complex architecture, including an engine and one or more electric motors and/or generators, may require knowledge of the speed at which each of the torque generating devices is operating. In addition, devices such as motors and generators can often rotate in either of two directions. Thus, in addition to the speed of a device such as a motor or generator, it may also be important to know the direction in which the device is rotating. The combination of speed and the direction of rotation is the velocity of the device, a knowledge of which is useful to control the vehicle.
Because of inaccuracies in measurement devices, such as sensors, and in communications links, such as a controller area network (CAN), sensor measurements may need to be validated to ensure their accuracy. Validation of the velocity of a torque generating device may require two independent speed measurements. The cost of providing a vehicle with two separate speed sensors for each torque generating device may be unacceptably high. Therefore, a need exists for a system and method for validating velocities of torque generating devices, such as engines and motors, in a vehicle, wherein the velocities can be validated using a single speed or velocity sensor for each torque generating device, and using a knowledge of the relationships between the speeds of the devices based on the vehicle architecture.